Thermal insulation batts are often comprised of a relatively thick layer of low density bulk insulating material, such as fiberglass wool, faced with for instance asphalt-coated kraft paper facing. The asphalt coating is used both to adhere the layer of thermal insulation to the facing and also to provide vapor barrier properties to the paper. Alternatively, foil-backed paper can be attached to the fiberglass wool with a thin coat of asphalt. Another approach to vapor retardance is to apply a separate 4- to 6-mil polyethylene film over installed insulation. Guardian Fiberglass, Inc. produces a polypropylene scrim kraft for insulation applications.
Such insulation products are generally provided in the form of continuous lengths (packaged as rolls) or of individual panels, or batts, with facing materials on one or both major surfaces to enable the insulation product to be handled more easily and to be fastened in position for insulating purposes, and to minimize dusting of the fiberglass fibers within the insulation product. In most instances, the provision of a facing that forms a vapor barrier is desirable in order to prevent water vapor passing through the insulation product and condensing on a cold surface.
Facing materials may be adhered to the fiberglass fiber blanket in a number of ways. For example, solvent-based or water-based adhesives or hot-melt adhesives may be applied to the facing material or to the surface of the fiberglass wool blanket, with the fiberglass wool blanket and the facing material then being brought together to surface bond the two materials. Alternatively, the facing material itself may be rendered adhesive before application to the fiberglass wool blanket. For example, a thermoplastic material such as a synthetic polymer or a bituminous layer on one surface of the facing material may be heat softened for that purpose. However, the heat treatment of polyethylene—the most commonly used synthetic polymer in this context—may destroy any water vapor barrier properties it possesses.
A product which has met with some commercial success is a kraft paper/polyethylene vapor barrier manufactured by Owens Coming, which is bonded via the polyethylene to a glass wool blanket. A more sophisticated product consists of an aluminum foil/kraft paper vapor barrier adhesively bonded on its kraft paper surface to a glass wool blanket. However, the aluminum foil incorporated as the vapor barrier renders it much more expensive.
The organization known as ASTM has published—under the designation E 96-00 (published July 2000)—a description of test methods to determine water vapor transmission of materials through which the passage of water vapor may be of importance, such as paper and other sheet materials. Those test methods permit the determination of PERM values for the sheet materials. The PERM values reflect the water vapor transmission and permeance of the materials.
Many conventional insulation facing products fail to consistently meet PERM requirements. PERM values greater than 1.0 are considered unacceptable for the purposes of the present invention.
Fire retardant facing material is also used on insulation products. Typical fire retardant facings consist of foil skim Kraft paper; a Kraft paper facing with a thin foil bonded to it. However, these facing materials are expensive, they require specialized adhesives and a very controlled manufacturing process to produce.
There is a need for an insulation product having a flexible kraft laminate which is inexpensive and fire retardant.